One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(5,7)(6,8)(9,10,12,14)(11,13,16,15)(25,26)(27,33)(28,36)(29,30)(31,34)(32,37)(35,38)(39,40)(1,3,5,8)(2,6,7,4)(9,10)(11,15)(12,14)(13,16)(18,22)(23,24)(26,30)(27,34)(28,37)(38,39)(3,8)(4,6)(9,10,12,14)(11,13,16,15)(17,18)(19,23)(20,24)(21,22)(25,27)(26,31)(28,35)(29,34)(30,33)(32,38)(36,39)(37,40)(1,4)(2,3)(5,6)(7,8)(9,10)(11,13)(12,14)(15,16)(17,19,21,20)(18,23,22,24)(25,26)(27,33)(28,32)(29,30)(31,34)(35,39)(36,37)(38,40)(1,2)(3,4)(5,7)(6,8)(9,11,12,16)(10,13,14,15)(17,20,21,19)(18,24,22,23)(25,28,29,37)(26,32,30,36)(27,35,34,40)(31,38,33,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.